This invention relates to shipping containers and more particularly to shipping containers for rolls of flexible sheet or film material.
The shipment of rolls of plastic sheet and film in corrugated boxboard cartons is a widespread practice. The plastic film is wound around a thin hollow cylindrical core and is supported at its ends by a pair of end plates. The end plates are square with each side slightly longer than the outer diameter of the roll, and incorporate a plug for inserting into the core, so that the entire weight of the roll is carried by the end plates. The carton is usually square, and the length of the carton or box is equal to or greater than the length of the roll. Dunnage is used to fill the ends of the carton when the length of the carton is greater than the length of the roll being shipped. A representative roll and carton of this type are shown in U.S. Pat. No. 3,710,539. For shipping, a plurality of rolls (usually 4 to 9, depending on the size of a roll), packaged in boxboard cartons as described, are placed on a pallet. The rolls are usually stacked either 2 or 3 high, and a divider sheet, which is typically made of plywood or fiberboard, is placed between adjacent of cartons. The cartons are stacked so that the end plates are aligned. In this way the entire weight of rolls in each stack is transmitted through the end plates to the pallet. The pallet and divider sheet may have cleats to maintain the cartons in alignment. The entire pallet load is unitized in some manner such as strapping or shrink wrapping.
Packages of rolls in boxboard cartons as above have several disadvantages.
First, boxboard cartons and their contents can be damaged in various ways. There is a danger of crushing a box and damaging its contents due to shifting of a pallet load in transit. The conventional corrugated boxboard carton is not strong enough to withstand the loading imposed by the end plates of a carton stacked thereon. While the cartons are initially stacked so that the end plates of all cartons in a stack are aligned, it is difficult to maintain this precise alignment throughout shipment. The use of a divider sheet lessens but does not entirely eliminate crushing. Cartons can also be damaged by tearing due to the use of metal strapping.
Second, a plant that ships a number of widths of roll goods must either maintain an equal number of lengths of shipping cartons or use dunnage, neither of which is entirely satisfactory. The former requires a large inventory of cartons. The use of dunnage is not desirable because the dunnage may contaminate the plastic film and because the presence of end plates at positions other than the ends of the carton increases the possibility of carton failure under the end plates due to misalignment of the end plates.
Third, the conventional boxboard packaging entails the use of considerable quantities of non-reusable materials. The boxboard carton and the divider sheet are not reusable, and the pallet is frequently not returned or reused. The use of non-reusable packaging materials in quantity present a waste disposal problem and is ecologically undesirable.
Rigid shipping containers for rolls of flexible sheet material are also known. For example, U.S. Pat. No. 3,489,274 shows a rigid container for a plurality of rolls comprising a plurality of spaced rigid rectangular horizontal members and a plurality of vertical end plates (one pair for each roll) which are supported by the horizontal members. Transverse cleats at or near the ends of the horizontal members retain the end plates in place and prevent longitudinal slippage of the rolls, and longitudinal cleats prevents lateral slippage. U.S. Pat. No. 3,858,723 shows an adjustable and reusable pallet for coiled sheet metal comprising a pair of independent pallet decks, each of which has upturned side walls that are tangential to the material.
In my copending application Ser. No. 552,069, filed Feb. 4, 1975, now U.S. Pat. No. 4,042,107, issued Aug. 16, 1977, I have shown and described a returnable shipping container which is able to support a roll of any length up to slightly less than the length of the container without the use of dunnage. The container includes upper and lower rigid pallets, each of which has uniformly spaced holes arranged in a plurality of longitudinal rows, and a pair of end plate assemblies which have dowels that are received in these holes. This arrangement of holes makes it possible to place each end plate assembly in any one of a number of positions so that the distance between end plates can be varied in accordance with the length of the roll being shipped. A finite number of spacings between end plates are provided for in this manner. Each end plate assembly includes an end plate, a threaded plug or shaft, and a compression disc supported by the shaft and movable toward or away from the end plate. The discs engage the ends of the roll and hold the roll in compression. These movable discs provide an infinitely variable adjustment so that a roll of any length up to the maximum provided for can be supported. An asymmetrical pallet leg configuration permits stacking of containers one above the other. The pallets are nestable, which facilitates their return to the shipper.
The containers of either U.S. Pat. No. 3,489,274 or my copending application offer greater protection against accidental damage to rolls by bending or puncturing than that afforded by boxboard cartons. Also, the containers of either U.S. Pat. No. 3,489,274 or my copending application can be stacked vertically without damaging the rolls. However, rolls shipped in these containers are exposed to dust unless the containers are covered or wrapped (e.g., by shrink wrapping), and are subject to possible damage by the tines of a fork lift truck.